This intentionally doesn't document the third party network aspect of the endpoint. This is scheduled for a later area for dealing with third party network/IDs and is reported as https://github.com/matrix-org/matrix-doc/issues/1476
The client-server response has been broken out to a shared file: both the client-server and server-server /publicRoom endpoints return the same thing, with slightly different inputs.
The inputs (and behaviour) are based upon the docstring here: 43ecfe0b10/synapse/federation/transport/server.py (L583-L612)
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